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Raman study of a highly altered basalt -- AKB

igneous mineralogy, alteration products, & a microorganism

A Martian analog rock, a 1.1 billion-year-old Keweenawan basalt (AKB). This rock is a highly altered basalt found in a creek.  It has a fine-grained reddish matrix with small "clots" of a grayish-green clay mineral and coarse amygdules filled with light-colored minerals. Two surfaces of this rock are studied:
heavily altered original surface, with surface relief of several mm. roughly cut flat surface , unpolished.

Mineral phases found in this rock:

The dark red matrix of the altered basalt yielded spectra of hematite (alpha-Fe2O3), plagioclase, saponite,  and pyroxene. The mineral phases inside the large, white amygdules are mainly calcite (CaCO3) and thomsonite (a type of zeolite). some rare phases -- microorganism, anatase, quartz, and K-feldspar

Mineral distributions and mineral proportions:

Successive Raman spectra along two traverses cross from the matrix to amygdules and back. Mineral modes obtained based on automated traverses on the original and sawn surfaces
Compare the two linear traverses, one with focus adjustment at each point, one without.  Basic mineral distributions are the same. Mineral modes obtained from the original surface Mineral modes obtained from the sawn surface

Reference:  Wang A., Jolliff B. L., Haskin L. A., “Raman spectroscopic characterization of a highly weathered basalt – igneous mineralogy, alteration products, and a bug”, Twenty-ninth Lunar and Planetary Science Conference, 1998.
                        Wang A., Jolliff, B.L., and Haskin L.A. (1999) Raman spectroscopic characterization of a highly weathered basalt: igneous mineralogy, alteration products, and a microorganism, J. Geophys. Res., 104, 27067 -27077.

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